The purpose of this project is to study the function of single units in the Ventral Lateral Geniculate Nucleus (LGNv) of the cat and to further determine the afferent projections to this structure from within the brain. Single units in LGNv are recorded with tungsten electrodes and visual receptive fields plotted on a tangent screen utilizing standard techniques. The patterns of cell firing in response to various stimuli are specified in a quantitative fashion with the collection of peristimulus time histograms. It is planned to further evaluate the function of single units in LGNv by reversibly cooling the two primary visual areas of the brain which project to this structure, the ipsilateral visual cortex and superior colliculus. Horseradish perioxidase is injected into the LGNv and various control areas and the retrograde transport of this material into neuronal cell bodies in various locations studied by light microscopy in stained and unstained serial sections after benzidine reaction. Areas projecting to LGNv thus identified have included several areas of ipsilateral visual cortex, contralateral LGNv, ipsilateral Superior Colliculus, Dorsal Median Raphe nucleus, locus coeruleus, and areas in hypthalamus.